What is a GLP-3? GLP-3 drugs, explained

If you’ve looked into weight loss medications online, your algorithm may also be showing you videos from so-called GLP-3s. So, what is a GLP-3? Is it the next big thing in medical weight loss? Maybe, but it’s not actually called a GLP-3. Read on as we explain.

A GLP-3 is not a real hormone, weight loss peptide, or drug class. It’s actually a misnomer being used to describe retatrutide, an injectable medication currently under development by Eli Lilly for weight loss and type 2 diabetes. The proper name for retatrutide is a triple-hormone receptor agonist, but you may see people referring to it as a GLP-3 instead.

See if you qualify

When people call retatrutide a GLP-3, they’re probably referring to the fact that it targets three hormone receptors: glucagon-like peptide 1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and glucagon (GCG). This triple-hormone receptor agonist ability makes retatrutide unique.

To date, hormone-based medications for weight loss have only targeted one or two receptors, including:

•  GLP-1 — as is the case with semaglutide (Wegovy, Ozempic) and orforglipron (Foundayo)

• GLP-1 and GIP — as is the case with tirzepatide (Zepbound, Mounjaro)

Retatrutide is different because, in addition to acting on the  GLP-1 and GIP receptors, it also acts on glucagon, which burns fat, increases calorie expenditure, and may lead to increased weight loss and better blood sugar control.  

Because retatrutide targets three hormones, people are calling it a GLP-3. But this isn’t technically correct, and it’s not a term used by the medical community. The “1” in GLP-1 does not refer to the number of hormones it targets. Rather, it’s part of the name of the hormone itself: glucagon-like peptide 1. 

And dual receptor agonists like tirzepatide are not called GLP-2s. They’re called GLP-1/GIP receptor agonists in honor of the two hormone pathways they target. (Not as sexy as a GLP-2, we admit.)

So, the correct name for retatrutide, per Eli Lilly, is a triple-hormone receptor agonist or triple-receptor agonist. You could probably also call it a GLP-1/GIP/GCG receptor agonist, but that’d be quite a mouthful!

Yes. GLP-2 medications mimic a hormone called glucagon-like peptide-2, or GLP-2 for short. 

Despite the similarity in name with GLP-1s, GLP-2s have nothing to do with promoting weight loss or controlling blood sugar levels. Instead, they support intestinal health in people with short-bowel syndrome. (This is a condition where the small intestine is shorter than normal, affecting its ability to properly absorb nutrients from food.) 

Today, there is one GLP-2 medication available: Gattex (teduglutide). 

It’s possible that when you hear people say “GLP-2,” they’re actually referring to dual GLP-1/GIP receptor agonists like tirzepatide (Mounjaro, Zepbound). Because these medications mimic two hormones, people may call them GLP-2s, even though — as we reviewed above — the number does not refer to the number of hormones these drugs mimic.

Similarly, dual GLP-1/GIP receptor agonists like tirzepatide are often lumped in with GLP-1s as a drug class, despite being chemically distinct. The ability to target two hormone pathways differentiates tirzepatide from single GLP-1 receptor agonists like semaglutide. 

However, GLP-1s were developed first, which may explain why we call the entire drug class GLP-1s (even if it also includes dual- and, perhaps one day, triple-receptor agonists). Also, since both drugs treat conditions like obesity and type 2 diabetes, it arguably makes sense to discuss them as the same drug class — unlike actual GLP-2s, which treat a condition that’s altogether different.

Triple-hormone receptor agonists, or “GLP-3s,” as social media sometimes calls them, work similarly to GLP-1s and “GLP-2s” (which are more accurately called dual-receptor agonists). By mimicking hormones naturally produced by the body, these medications help to lower blood sugar and body weight when used in combination with diet and exercise. 

Research has already shown that dual GLP-1/GIP agonists are more effective than single GLP-1 receptor agonists for weight loss. Given the research on retatrutide thus far, adding a third receptor into the mix may be even more effective. 

Here’s a quick look at the main similarities and differences of “GLP-3s” vs. GLP-1s vs. “GLP-2s”:

The earliest a “GLP-3” could be available would be mid to late 2027 or even early 2028. 

Eli Lilly announced plans to submit the triple hormone agonist retatrutide for FDA approval in the first quarter of 2027, Reuters reports. The FDA approval process takes 6–10 months. So, it may be possible to get retatrutide as soon as July 2027 or as late as January 2028.

See if you qualify

Now you know the latest on GLP-3s, including the fact that it’s not quite correct to call them (including the still-being-studied retatrutide) that. Here’s a quick recap on the correct lingo and meaning:

• A GLP-1 is a drug that mimics one hormone: glucagon-like peptide 1 (GLP-1). Examples include semaglutide, liraglutide, orforglipron, and dulaglutide.

• A GLP-2 can refer to one of two things: GLP-2 medications that treat short bowel syndrome or dual GLP-1/GIP receptor agonists like tirzepatide that treat obesity and type 2 diabetes.

• A GLP-3 is an unofficial nickname for triple-hormone receptor agonists like retatrutide, a drug currently under development by Eli Lilly. This medication mimics three hormones: GLP-1, glucose-dependent insulinotropic polypeptide (GIP), and glucagon.

• Early research suggests triple-hormone agonists (sometimes mistakenly called “GLP-3s”) may be more effective for weight loss than single GLP-1 agonists or dual GLP-1/GIP agonists.

• As of publication, Eli Lilly plans to submit retatrutide for FDA approval in early 2027. If approved, it will be the first triple receptor agonist on the market.